Evenly Matched has no once per turn restrictions. As long as its still the end of the Battle Phase and your opponent controls more cards than you, you can activate a second (or even a third) copy of Evenly.
Can you activate 2 evenly matched?
Since Evenly Matched will resolve while you control it, your opponent will usually end up keeping at least one card. This means that you can activate Evenly Matched on your first turn if you go second and banish most of your opponents cards!
Can I skip my main phase 2?
A player entering their Battle Phase is optional after their Main Phase 1 ends, except when card effects mandate it. However, if card effects skip the same players Main Phase 1 and Battle Phase during the same turn, that player cannot enter their Main Phase 2 and must instead proceed immediately to their End Phase.
Can you activate spells during main phase 2?
Activate Spell/Trap Cards of any Spell Speed. Quick-Play Spell Cards and Trap Cards cannot be activated in the turn they are Set.
Can you change a monster to Defence in Main Phase 2?
A monsters battle position can be changed in one of two ways: manually or by card effect. During an open game state in the Main Phase, the turn player can manually change the battle position of any individual monster they control. Face-down Defense Position monsters are always flipped when changed to Attack Position.